In everyday life causal attribution is important in order to structure the complex world, provide explanations for events and to understand why our environment interacts with us in a particular way. This study used functional magnetic resonance imaging (fMRI) in 30 healthy subjects to separate the neural correlates of self vs. external responsibility for social events and explore the neural basis of self-serving attributions (internal attributions of positive events and external attributions of negative events). We presented short sentences describing positive and negative social events and asked participants to imagine the event, to decide the main cause and assign it to one of the categories (internal vs. external). FMRI data were analyzed using a 2 x 2 factorial design with the factors emotional valence and attribution. Internal compared to external attribution revealed activations along the right temporoparietal junction (TPJ). The reverse contrast showed a left lateralized network mainly involving the TPJ, the precuneus and the superior/medial frontal gyrus. These results confirmed the involvement of a fronto-temporoparietal network in differentiating self and external responsibility. Analysis of the self-serving bias yielded activation in the dorsal anterior cingulate and in the dorsal striatum, suggesting a rewarding value of these attributions.